This invention relates to apparatus for joining pipes, and in particular, to piping joints that are indexable and that can be disassembled.
Pipes and piping systems are useful in a wide variety of applications. Piping systems for transporting or routing solids, liquids and gasses, for example, are virtually ubiquitous throughout home and industry. When installing a piping system, individual pipes are typically acquired, in set lengths, and must be assembled by cutting and joining the pipes to produce the desired piping configuration. Different applications may present different pipe joint requirements. In most applications it is important that the pipe joints be strong, so that they do not become a failure point for the piping system. This is particularly important when the joints are not easily accessible. In some applications, easy disassembly of the piping joint is desirable, for example in applications where the piping system is temporary and will ultimately be removed, or in order to accommodate difficulties that might be encountered during field assembly. Also, in many applications it is important that the pipe joints be sealed, either to prevent whatever is in the piping system from leaking out, or to prevent external fluids from leaking into the pipe system, or both.
It is sometimes desirable to have a pipe joint that will rotationally index the pipes being joined. For example, inclinometers are frequently used in geological applications to detect movement of a hillside or other geologic formation. Inclinometers measure inclination relative to the vertical axis, and periodic measurements taken along a conduit installed in the ground can be compared to detect changes. Typically a plastic pipe conduit is installed in a bore hole in a generally vertical orientation. The plastic pipe conduit includes oppositely disposed longitudinal grooves along its inner surface that provide a track for the inclinometer, which records inclination while being lowered through the plastic conduit. Because the profiled pipe conduit is constructed by joining a number of separate pipes, the individual pipes must be rotationally aligned, or indexed, so that the longitudinal grooves in the profiled pipes form a continuous track along the length of the pipe conduit.
Many different systems have been developed to facilitate assembling and joining pipes, which systems may be more or less suitable for any given application. For example, home water systems employing copper piping is typically installed using sleeve joint elements that are soldered to the pipe. This produces a strong, reliable and generally permanent pipe joint. Home irrigation systems, on the other hand, typically employ plastic piping that is joined using male and female joint elements that are glued together. This type of piping system is very flexible, easily installed and relatively inexpensive. Neither of these methods allow for easy disassembly of the piping joints.
A threaded joint for tubular plastic parts is disclosed in U.S. Pat. No. 5,906,398 to Larsen et al. Larsen et al. teaches the use of helical threads wherein at least one of the threads terminates abruptly, creating a transverse end-surface that can be located at a predetermined position. This end-surface functions as a stop, whereby the pipes are rotationally oriented in a desired manner when the joint elements are fully screwed together. It may be difficult, however, to control the fabrication of threads well enough to achieve precise rotational control over the joined pipes. In addition, difficulties may arise in field applications where dirt and other foreign matter may interfere with the threaded joint, or may prevent the joint from fully closing thereby failing to accomplish the desired rotational orientation.
In U.S. Pat. No. 5,015,014 to Sweeney, a plastic pipe section is disclosed wherein matching internal and external rabbets are formed on the pipes to be joined, and the pipes are pressed together. An optional clamp may be installed around the joint to help strengthen the joint. This type of joint, which relies on the flexibility of the pipe to allow the interlocking ribs to pass each other, may not provide a sufficiently strong joint for certain applications. Also, the force required to join the pipes in interlocking fashion may make assembly difficult or require special tools, and dirt encountered in the field may interfere with assembly of the joint.
U.S. Pat. No. 5,915,738 to Guest and U.S. Pat. No. 5,029,904 to Hunt both disclose pipe joints wherein one pipe is provided with a circumferential ridge and the mating pipe is provided with a mating cup or fingers having a lip that engages the circumferential rib to hold the pipes together. These types of joints may not provide sufficient strength for certain applications, and result in a joint having a diameter greater than the diameter of the pipe, which may be undesirable.
In U.S. Pat. No. 5,176,406 to Straghan, a pipe coupling is disclosed for joining pipes in end-abutting relation comprising a sleeve having outwardly deflectable segments that engage circumferential grooves on each of the pipes. In addition, an additional slot is provided on the coupling member to engage a raised button provided on the pipes, thereby allowing the pipes to be rotationally aligned in a predetermined orientation. Joints of this type may not be strong enough for certain applications, and the joint will have a larger diameter than the pipes. The joint is also difficult to disassemble. The slot is also susceptible to being clogged by dirt and other foreign matter encountered in the field, interfering with pipe assembly. Also, the longitudinal slots at the joint will weaken the torsional rigidity of the joint, which could result in a weaker joint and/or rotational misalignment of the pipes.
There is a need for a strong pipe joint that is sufficiently robust to tolerate dirt that may be encountered in the field, and that can be disassembled. There is also a need for a robust pipe joint that is indexable.
The present invention is directed to a joint for connecting pipes comprising a male joint member having a plurality of outwardly-extending locking tabs at its distal end and a female joint member having a plurality of inwardly-extending locking tabs spaced between its distal and proximal ends, wherein the outwardly-extending locking tabs can slide past and then be rotated to a position behind the inwardly-extending locking tabs such that the locking tabs prevent relative axial motion between the male and female joint members. In another aspect of the invention, the joint further comprises a rotational locking apparatus that engages to prevent relative rotational motion between the male and female joint members.
According to another aspect of the invention, the rotational locking apparatus comprises a locking pin having a cylindrical portion extending outwardly from the male joint member that engages a circular aperture on the female joint member.
In one embodiment, the locking pin has a chamfered profile whereby the female joint member can more easily slide over the locking pin.
In yet another aspect of the invention, the locking tabs further comprise interlocking reverse-chamfered edges wherein the inwardly-extending locking tabs radially interlock with the outwardly-extending locking tabs.
In still another aspect of the invention, the male joint member may further comprise internal longitudinal grooves that match longitudinal grooves in the pipes that are to be connected.
In another aspect of the invention, the joint may further include an O-ring that is installable to seat between the male joint member and the female joint member.